Spacewalks set to fix space station cooling pump

By Matt Smith, CNN

Updated 1512 GMT (2312 HKT) December 20, 2013

Photos: International Space Station13 photos

International Space Station – The crew of the space shuttle Atlantis took this picture of the International Space Station after leaving it in July 2011. Atlantis was the last shuttle to visit the station, which was first launched in 1998 and built by a partnership of 16 nations.

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International Space Station – The crew of the space shuttle Endeavour initiates the station's first assembly sequence in 1998. The International Space Station includes several large modules, each launched separately and connected in space by astronauts.

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International Space Station – The Zarya control module, on the left with the solar panels, floats above Earth with its newly attached Unity module after the first assembly sequence in December 1998.

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International Space Station – The first crew of the International Space Station, seen on board in December 2000. From the left are cosmonaut Yuri P. Gidzenko, astronaut William M. Shepherd and cosmonaut Sergei K. Krikalev.

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International Space Station – The Endeavour crew installs the first set of U.S. solar arrays on the station in 2000.

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International Space Station – In March 2001, a space shuttle delivered the station's second crew and brought the first one home. It also brought Leonardo, the station's first Multi-Purpose Logistics Module, to the station. Leonardo carried supplies and equipment.

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International Space Station – In September 2006, the space shuttle Atlantis docked with the space station, delivering solar wings and a new truss.

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International Space Station – The space shuttle Discovery leaves the space station in March 2008 after its crew successfully delivered and installed the Japanese-built Kibo lab.

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International Space Station – The unmanned SpaceX Dragon spacecraft connects to the space station in May 2012. It was the first private spacecraft to successfully reach an orbiting space station.

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International Space Station – An unmanned Russian cargo craft disconnects from the space station in April 2013. The station relies heavily on ships to bring up supplies.

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International Space Station – Commander Koichi Wakata of the Japan Aerospace Exploration Agency peers out of the space station's Cupola observatory on April 27. The Cupola is a dome-shaped module that allows station crew members to observe and guide activities outside the station.

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International Space Station – A Russian Soyuz spacecraft is docked with the space station on May 5. Since the U.S. shuttle program ended in 2011, all crew members are ferried to and from the space station on Russian rockets.

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International Space Station – A Soyuz spacecraft is seen on May 13 as it lands in Kazakhstan with Wakata and other members of the his Expedition 39 crew.

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Story highlights

Three spacewalks are planned to fix failed coolant pump

Two astronauts will take part in the spacewalks

The failed pump forced controllers to scale back some station operations last week

Astronauts will conduct a series of Christmas-week spacewalks to replace a faulty coolant pump aboard the International Space Station that has forced operations to be scaled back since last week, NASA announced Tuesday.

Two astronauts, Mike Hopkins and Rick Mastracchio, will start work outside the station on December 21, with follow-up spacewalks scheduled on December 23 and 25. The goal is to take out the pump that shut down December 11 and replace it with a spare already on board, the U.S. space agency announced.

The pump circulates ammonia through loops outside the station to keep equipment cool. The space station's life support system is up and running, but ISS operations were cut back as a result of the failure, NASA said.

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The station currently houses six people. In addition to Mastracchio and Hopkins, Russian cosmonauts Mikhail Tyurin, Sergey Ryazanskiy and Oleg Kotov and Japanese astronaut Koichi Wakata make up the Expedition 38 crew.

The job will force NASA to put off the first commercial supply mission by Orbital Sciences Corp.'s unmanned Cygnus spacecraft, which was successfully tested in September. The launch had been scheduled for Thursday, but has been pushed back to at least January 13, the company and NASA announced.